1. Field of the Invention
The present invention relates to a method and apparatus for encapsulation of a liquid or meltable solid material, more particularly, it relates to a method and apparatus for producing microcapsules filled with a liquid or meltable solid material.
2. Description of the Prior Art
U.S. Pat. No. 4,251,195 discloses an apparatus for producing miniature capsules which comprises a capsule-forming orifice defined by open ends of two coaxial conduits. When producing material-filled capsules with this apparatus, a material to be encapsulated and a capsule-forming material are heated to a temperature not less than a melting point of the capsule-forming material and then fed to the capsule-forming orifice to form a coaxial composite jet. The resultant composite jet is introduced into a flow of a cooling liquid material which flows downwardly in a capsule-forming cylinder arranged just beneath the capsule-forming orifice. The composite jet is formed into material-filled capsules by the interfacial tension of the materials. Although the aforesaid apparatus enables to produce material-filled capsules with a diameter of 0.5 to 5 mm, it is difficult to produce microcapsules filled with a high-melting material and having a diameter of 2 mm or less. Because, smaller the size of the capsule, greater the cooling rate of the material to be encapsulated, resulting in the solidification of the high-melting material before the formation of the microcapsules and blockage of the orifice due to the solidified high-melting material.